Question

Crossing over most commonly occurs during ______.

Options

• telophase II

• prophase II

• anaphase I

• prophase I

Answer 1

Crossing over most commonly occurs during prophase I.

Explanation:

Crossing over most commonly occurs during prophase I of meiosis. During this stage, homologous chromosomes pair up and exchange segments in a process called crossing over, which creates genetic variation. This involves the physical exchange of chromosome segments between non-sister chromatids at points called chiasmata, allowing recombination of genes. This process does not occur during the later stages such as anaphase I or prophase II, but specifically during the early prophase I when chromosomes are closely aligned.